Thailand's first tropical storm in three decades killed one person on Friday as it arrived on the south coast, knocking down trees and blowing off roofs in its path, but was losing speed, officials said, while warning against the risk of flash floods.

Accompanying winds churned up high waves and gusts in the Gulf of Thailand as tropical storm Pabuk made landfall in the Pak Phanang district of Nakhon Si Thammarat province, where trees crashed down on houses to cause widespread damage.

Disaster mitigation officials said the person killed was among the crew of a fishing boat that capsized in strong winds near the coast of nearby Pattani province. Another of the crew was missing, but four others were safe.

Weather officials warned of torrential downpours and strong winds in 15 provinces in the Thai south, home to one of the world's largest natural rubber plantations and several islands thronged by tourists.

But by Friday afternoon, the storm was slowing, and was heading for the province of Surat Thani, the Thai Meteorological Department said in a statement.

"It is expected to downgrade to be a tropical depression," it added. "People should beware of the severe conditions that cause forest runoffs and flash floods."

The conditions are expected to persist into Saturday. With airports and ferry services shut, people were advised to stay indoors until the storm passed.

The National Disaster Warning Center also sounded alarms around tourist beach destinations, such as Koh Samui and Koh Phangan, urging people to leave high-risk areas for higher ground.

During the past few days, 6,176 people have been evacuated to shelters from Nakhon Si Thammarat as well as the provinces of Pattani, Songkhla and Yala, the Department of Disaster Prevention and Mitigation has said.

The Nakhon Si Thammarat airport said it had closed, and low-cost Nok Airlines Pcl said it had cancelled all eight flights to and from the province.

The Surat Thani airport will also close from Friday afternoon to Saturday, cancelling flights by Nok Airlines, Lion Air, and Thai Smile, a subsidiary of national carrier Thai Airways.

Earlier, Bangkok Airways Pcl said it had canceled all flights to and from the holiday destination of Koh Samui, where ferry services have also been suspended.

National energy company PTT Exploration and Production Pcl said it had suspended operations at Bongkot and Erawan, two of the country's biggest gas fields in the Gulf of Thailand.